Method of imparting wrinkle resistance to fabrics

ABSTRACT

A yarn structure is provided that imparts improved wrinkle resistance in fabrics produced therefrom. The yarn is composed of plurality of filaments or strands that are intermittently connected or fused by an essentially permanent bond, i.e., analogous to spot welding, along their lengths. The appropriate distribution of these points of bonding, preferably varying from a distance of about 20 filament diameters as an upper limit to a frequency of about one in 2,000 filament diameters measured along the length of the fiber as a lower density limit, is obtained by removing any size, lubricant or finish from the fiber, applying an electrical charge, and spraying or otherwise applying a thermoplastic polymer to the surface of the fiber. Droplets of the applied polymer adhere to the fiber and provide effective jointer points between adjacent fibers.

llnited States Patent [72] Inventors George E. R. Lamb Mendham; Dusan C. Prevorsek; Hendrikus J. Oswald, both of Morristown, all of NJ. [21] Appl. No. 41,407 [22] Filed May 28, 1970 [45] Patented Jan. 11, 1972 [73] Assignee Allied Chemical Corporation New York, N.Y.

[54] METHOD OF IMPARTING WRINKLE RESISTANCE T0 FABRICS 9 Claims, 1 Drawing Fig.

[52] U.S.Cl 156/166, 156/180,156/291,8/130.1, 8/115.6,117/93.4, 117/105.3, 161/143, 161/146 [51] Int. Cl B32b 5/02 [50] Field of Search 156/166, 180, 291, 272, 290; 117/934, 105.3;8/1155, 115.6,130.1;161/143,146

[5 6] References Cited UNITED STATES PATENTS 2,647,851 8/1953 Schwartz l6l/l43X 3,148,999 9/1964 Hoffman et a1 8/1 30.1 X 3,152,919 10/1964 Bileset a1. 8/1301 X 3,369,948 2/1968 Ostmann 161/143 X Primary Examiner-Alfred L. Leavitt Assistant Examiner-J. H. Newsome Attorneys-Arthur J. Plantamura and Herbert G. Burkard ABSTRACT: A yarn structure is provided that imparts improved wrinkle resistance in fabrics produced therefrom. The yarn is composed of plurality of filaments or strands that are intermittently connected or fused by an essentially permanent bond, i.e., analogous to spot welding, along their lengths. The appropriate distribution of these points of bonding, preferably varying from a distance of about 20 filament diameters as an upper limit to a frequency of about one in 2,000 filament diameters measured along the length of the fiber as a lower density limit, is obtained by removing any size, lubricant or finish from the fiber, applying an electrical charge, and spraying or otherwise applying a thermoplastic polymer to the surface of-the fiber. Droplets of the applied polymer adhere to the fiber and provide effective jointer points between adjacent fibers.

ales-341163 PATENTEU mu 1 I972 i ii I! I m METHOD OF IMPARTING WRINKLE RESISTANCE TO FABRICS CROSS-REFERENCES TO RELATED APPLICATIONS The present invention is an improvement over the invention disclosed in our copending application Ser. No. 854,469, entitled Fabrics With Improved Wrinkle Resistance, filed on Sept. 2, 1969.

BACKGROUND OF THE INVENTION This invention relates to fabrics having a high degree of a combination of freedom from wrinkling, capacity to retain a pressed crease, ability to undergo washing without the need for subsequent ironing, and prolonged retention of a freshly pressed look.

These properties are commonly achieved in the prior art, for example, by making a fabric from a blend of a synthetic fiber and a natural fiber, and subsequently treating the fabric with one of many known chemical agents, which reacts with the natural fiber so a to improve its wrinkle resistance and with it that of the fabric. This method is widely used, but it possesses a number of disadvantages. One disadvantage is the necessity of using staple fibers in order to make possible the blending with the natural fiber. A second disadvantage is the poor abrasion resistance sometimes found in fabrics treated in this fashion owing to the weakness of chemically treated cotton in this respect. A third disadvantage lies in the irreversible nature of the shape of the garment once the treatment has been completed. Thus, creases, once they are set in the fabric, can never be ironed out while new creases cannot be ironed into the garment. This third disadvantage has precluded the use of such fabrics whenever the garment must be altered to fit the customer.

Another method comprises making the fabric from a yarn that has been texturized, that is to say, a yarn that has been subjected to a process which changes each filament in the yarn from a more or less straight shape to a zigzag or wavy shape when the construction of fabric is correctly chosen, a,successful wrinkle-resistant fabric can be obtained using sri-ch texturized yarns. However, use of texturized yarns is unattractive because of the high cost of the texturizing process.

Another approach resides in making the fabric particularly thick with respect to the diameter of the individual filaments in the yarn. This can be done by using yarns with a large number of filaments or by making so-called double knits." This method has the apparent disadvantage of being limited to knitted or relatively thick fabrics whose use is relatively small.

SUMMARY OF THE INVENTION According to the present invention, yarn can be produced which may be woven, knit or otherwise converted into fabrics which have superior resistance to wrinkling, superior ability to maintain a crease through repeated launderings and to preserve a freshly pressed appearance for long periods of time, and the capacity to permit changes in the shape of the fabric, if such a change is desired. The advantages of the invention are obtained by passing continuous filament yarn through a liquid, e.g., acetone, which removes any size, binder or antistatic agent that may be present, through a zone where the liquid is driven off, for instance by a current of hot air, then over a grounded metallic part where electric charges are deposited on the yarn, then through a zone where the electric charges cause the filaments in the yarn to repel one another. In this zone, a spray of a solution of a polymer is directed at the travelling yarn so that droplets of the spray impinge on the yarn and adhere thereto. The yarn then passes through a guide that unites the filaments and causes them to adhere in pairs or in groups of more than two either by virtue of the residual tackiness of the droplets or by passing the yarn through a heated zone where the particles of polymer become softened. It will be clear to those familiar with the handling of continuous multifilament yarn that some such adhesion contributes to the ease of further processing, which would otherwise suffer from the removal of finish as described above.

LII

The yarn is subsequently passed through a cooling zone and then wound up in the usual manner. This yarn is now ready for weaving or knitting into fabrics which will exhibit improved wrinkle resistance over similar fabrics made from yarn not treated according to the method described. The appearance of the fabric may be further enhanced by heat treatment while the fabric is held under slight tension, or alternately, once the garment has been made, it can be heat set over a form to whose shape the garment will thereafter permanently conform.

It is an object of the present invention to provide a method for producing fabrics with improved wrinkle resistance which comprises preparing the yarn from which the fabric is to be made so that the filaments within controlled limits adhere permanently to other filaments at some of the points where the filaments come in contact with one another.

It is another object of the invention to provide a method which comprises using an electrical charge to attract on the surface of the fiber droplets of polymer which serve as interconnecting points between adjacent fibers of a multifilament yarn for imparting a novel characteristic structure to yarn so that fabric produced therefrom has improved body and wrinkle resistance.

Additional objects and advantages will become apparent from the detailed description of the invention which follows taken in conjunction with the FIGURE of the drawing which depicts in greatly enlarged scale longitudinal sections of a yarn composed of a plurality of fibers which are intermittently bonded together. The single FIGURE of the drawing depicts schematically a yarn in which the several component fibers are spot-adhered at a plurality of spots.

DESCRIPTION of the PREFERRED EMBODIMENT A first requirement of the mechanism which serves to bind contiguous fibers in a network that enhances wrinkle resistance is that the droplets of the polymer solution which weld the adjacent fibers should be within a certain range of size. This can be verified by mixing a certain amount of dye with the solution, which is sprayed as droplets, and looking at the treated yarn, and more specifically at the thermoplastic resin welding droplets, with a microscope. The size of the dried droplets can then readily be seen. We have found that the method of the present invention will yield the desired improvements when the diameter of the dried droplet, i.e., the droplet after the solvent (if any is employed) has been driven out, is greater than one quarter the diameter of the filaments in the yarn (if the droplet is roughly spherical) or smaller than ten times the diameter of the filament in the yarn; the size of those particles may be suitably controlled such as by adjusting the pressure of the air which is fed to the spray, the flow of polymer solution which is fed to the spray, and the distance between the spray nozzle and the yarn. The size of droplets can be readily estimated by holding a microscope slide for about 1 second in the position to be occupied by the yarn and then by looking through a microscope at the droplets which have stuck to the slide to gain a good estimate of the size of particles which are being obtained.

Of equal importance is the number of these droplets or particles which are deposited in the yarn. We have found that a frequency of approximately one droplet on each filament for every 20 filament diameters measured along the filament is the upper limit for the density of junctions. Excess of this limit has been found, in most instances, to cause undue stiffening of the fabric. As a measure of the opposite extreme, we have found that a frequency of droplets below one on each filament for every 2,000 filament diameters on the average measured along the filament will fail to bring about the desired improvement to any significant degree. It is, moreover, important that the junctions formed between filaments by the spray particles should be strong enough to be essentially permanent, i.e., they should not break under the action of washing or creasing or the motion normally associated with use or the action of drycleaning fluids.

To this end, the polymer or agent which is used in the spray (forming the adhesive droplets) should be of such composition as to be compatible with the polymer composing the yarn, in addition to the requirement that it should be soluble in a volatile solvent. This may be achieved by the choice of one of several ways: the spray may consist of the same polymer comprising the yarn in a suitable solvent; or it may comprise the polymer composition comprising the yarn but in a form chemically modified to either reduce its crystallinity or increase its solubility; or again it may comprise a polymer composition other than that comprising the yarn but modified chemically so as to incorporate chemical groups that will make it compatible with the polymer comprising the yarn; or it may comprise a rubbery polymer which owes its adhesive strength to its flexibility; each of the above being dispersed in a suitable solvent. The choice of agent used in the spray may also depend upon the treatment ultimately intended for the fabric. Thus, the agent may comprise a polymer capable of taking part in further chemical reaction. The spray solution may then contain a catalyst or other reagent so that after the solution (i.e., droplets) has been applied to the yarn, the polymer cross-links either within itself or with the polymer of the yarn and thus confers permanency on the junctions. Alternately, the yarn may be fashioned into a fabric and then into the garments, and these may then be heat-treated on a mold or form and then exposed to a chemical agent that will cross-link the polymer in the junctions and confer permanence to whatever shape the garment may have acquired during the heat treatment.

The advantages of the invention may be applied to fabrics made from a variety of fibers including nylon 6, nylon 6,6, polyester, polyacrylonitrile, polyolefins, and the like, and blends thereof, and may in fact be applied to any fiber as long as the aforementioned conditions are fulfilled.

In addition to acetone as the medium which frees the fiber from any size, finish or coating, i.e., with which the fiber is treated before applying the electrical charge, any ofa variety of other organic liquids which do not substantially adversely affect the fiber in question may be employed such as methyl ethyl ketone, benzene, carbon tetrachloride, tri-chloroethylene, or any mixture thereof. The choice of such a solvent will evidently be ruled by considerations such as cost, toxicity, volatility, and absence of interaction between solvent and fiber, so that the solvent must not dissolve, swell or soften the fiber, all these considerations being readily understood by those skilled in the art who are familiar with the nature of polymeric fibers. Thus, acetone would be unsuitable for cellulose acetate fibers as also would be chloroform or ethyl acetate; carbon tetrachloride might cause some loss in strength in nylon fibers, and so on. Other unsuitable combinations may be readily learned by consulting published handbooks.

The liquid polymer which is applied to the surface of the fiber may comprise the same composition, or a blend including the composition of the fiber to be treated, or the polymer may be any of a variety of compatible polymeric compositions which adhere well and form a permanent bond with the treated fiber. Illustrative combinations of polymer and fiber, for example, are a solution of methoxy-methylated nylon 6,6 polymers dissolved in methyl alcohol and applied to any ofthe following fibers: nylon 6 or nylon 6,6; or rayon or cellulose acetate; or polyvinyl alcohol. Alternately, the polymer may be ethylene-propylene rubber dissolved in toluene and applied to polypropylene fibers or a solution of butadiene-styrene copolymer in benzene applied to nylon 6, nylon 6,6, polypropylene, rayon, cellulose acetate, or polyvinyl alcohol fibers.

An alternate means of applying an electric charge to the yarn consists of contacting the yarn with a metal object which is not grounded but electrically connected to a source of high DC voltage. The sign of this impressed voltage would be chosen so as to augment the magnitude of the charge which would normally be given the yarn by a grounded metallic object. Thus, if the yarn were normally to acquire a negative charge, the metal object should have a negative voltage applied to it. This magnified charge may also be used to increase the number of spray droplets which successfully impinge on a filament. The process of spraying an expanded yarn is necessarily inefficient, that is to say, only a fraction of the spray droplets adhere to the yarn, while the rest miss the filaments and are collected for reuse on a backplate or collector placed there for the purpose. If now the droplets are given a charge opposite in sign to that carried by the yarn, the attraction between droplets and yarn will work in favor of increased collision and will result in a more efficient transfer of material to the travelling yarn, this improvement being subject to proper adjustment of the relative velocity between yarn and spray, which relative velocity should be as low as possible.

Referring to the drawing, a number of filaments 10, ll, l2, l3 and 14 are shown in the longitudinal section. Not all points of contact between filaments are "welded" or glued. The points of contact which are not glued are shown at 15. Those points which are glued are shown at 16 between contiguous fibers intermittently located along the length of the fiber.

The following examples are illustrative of the invention. It will be understood, however, that the invention is not limited to the specific embodiments set forth by way of the examples. All parts are parts by weight unless expressly otherwise stated.

EXAMPLE 1 A. A nylon-6 yarn of 70 denier consisting of 32 filaments was passed through an acetone dip over a paper towel and unto a Godet roll rotating with a surface speed of 50 feet a minute. It then passed once around a grounded aluminum rod and onto a second Godet roll rotating with a surface speed of 54 feet per minute. Upon leaving the second roll, the electric charges deposited on the yarn by the aluminum rod caused the filaments to separate. The yarn traversed a length of 6 feet in this expanded form, then passed through a guide and onto a winder. At the center of the 6-foot expanded zone. a spray of solution was directed at the yarn. The solution contained 10 parts methoxy-methylated nylon 6,6, 30 parts water, 70 parts methyl alcohol, and 1 part blue dye. The spray was fed by air at 20 p.s.i. pressure and with solution at the rate of about l cubic centimeter/minute.

The yarn was found to carry an average of 10 spray droplets per millimeter, which is equivalent to one droplet per filament per l filament diameters. The yarn was tested for ability to recover from a crease by the following test (yarn recovery test).

A 5-inch length of yarn was tied in a loop and the loop placed over a rod 0.020 inch in diameter. A IO-gram weight was hung from the bottom of the loop. After 5 minutes, the sample was removed from the rod and a hairpin-shaped bight was cut off the end of the loop which had curved around the rod. This bight was placed on a device that measured the angle between the legs of the bight. After a further 5-minute interval, the angle was measured. In this kind of measurement, a reading of 180 indicates perfect recovery while 0 indicates the worst possible performance. The test was conducted in a 50 percent relative humidity atmosphere, and the samples were allowed ample time to come to equilibrium with the atmosphere before being tested.

in such a test, the yarn treated, according to the method described above, gave a reading of 169. Before treatment, the same yarn gave a reading of 132. The treated yarn was now knit into a sleeve, and this sleeve was placed over a cylindrical form and heat set by heating to C. for 15 minutes. This sleeve was visibly superior in resistance to wrinkling to a similar sleeve knit from untreated yarn and similarly heat set.

A separate section of this sleeve was placed over a conical form and simultaneously chemically and heat set by immersing in boiling 5 percent solution of citric acid for 20 minutes. On cooling, the sleeve maintained the conical shape even when immersed in the methanol-water mixture previously used as solvent for the polymer spray indicating that the spray polymer had become cross-linked.

B. The procedure of example 1(A) was repeated using instead in the spray solution substituted nylon 6 in place of substituted nylon 6,6 with similar results.

EXAMPLE 2 A polypropylene yarn of 100 denier and consisting of 50 filaments was treated as described in example 1. The spray solution was made from 5 parts of a butacliene-styrene copolymer and 100 parts benzene. The yarn recovery test gave a result of 165 for the treated yarn and 140 for the untreated yarn.

EXAMPLE 3 A rayon yarn of 100 denier and 22 filaments was treated as described in example l. The spray solution was made from parts of ethylene-propylene rubber, 100 parts toluene and 2 parts benzoyl peroxide. The yarn recovery test gave a result of 150 for the treated yarn and 130 for the untreated yarn. Lengths of knitted sleeve were made from both treated and untreated yarn. The sleeve made from treated yarn had a visibly improved wrinkle resistance over the untreated sleeve. The treated sleeve was placed over a conical form and placed in an oven at 150 C. for 1 minute. On cooling, the sleeve maintained the conical shape even when immersed in toluene indicating that the spray polymer had become cross-linked.

It will be understood that a wide variety of other fibers may be similarly treated so as to provide the structure taught by the present inventive concept. The invention therefore is not intended to be limited, except as set forth in the appended claims.

We claim:

1. A process for producing a fabric of improved wrinkle resistance which comprises initially freeing a textile multifilament yarn of any size, finish, or coating, thereafter applying to said yarn a substantially uniform electrical charge, allowing the filaments of the charged yarn to separate under the repulsive electrostatic forces effected by the electrical charge, applying a solution of a polymer in the form of separate droplets on the yarn thereby causing droplets of the solution to adhere to the filaments in spaced relation along the length of the filaments, and uniting the filaments by passing the yarn through a guide.

2. The process of claim 1, wherein the fiber is charged by passing it over a grounded metallic object.

3. A process as in claim 1 in which the diameters of the droplets adhering to the filaments after the solvent has been driven out are larger than one quarter the diameter of the filaments and smaller than ten times the diameter of the filaments.

4. A process as in claim I in which the number of droplets deposited on the filaments is greater than one for each filament for every 2,000 filament diameters measured along the filament and smaller than one for each filament for every 20 filament diameters measured along the filament.

5. A process as in claim 1 in which the spray solution comprises the same polymer from which the yarn is made dispersed in a suitable solvent.

6. A process as in claim 1 in which the spray solution comprises the polymer of which the yarn is made, but in a form chemically modified by substitution of side groups, so as to increase its solubility.

7. A process as in claim 1 in which the spray solution comprises a rubber polymer.

8. A process as in claim 1 which further comprises fabricating said yarn into a fabric, garment or article and heat setting the fabric, garment or article made from the yarn.

9. A process as in claim 8 wherein the solution of polymer is capable of cross-linking with itself or with the yarn, and which further comprises chemical treatment of the fabric, garment or article after, or in the process of, heat setting to cause said cross-linking. 

2. The process of claim 1, wherein the fiber is charged by passing it over a grounded metallic object.
 3. A process as in claim 1 in which the diameters of the droplets adhering to the filaments after the solvent has been driven out are larger than one quarter the diameter of the filaments and smaller than ten times the diameter of the filaments.
 4. A process as in claim 1 in which the number of droplets deposited on the filaments is greater than one for each filament for every 2,000 filament diameters measured along the filament and smaller than one for each filament for every 20 filament diameters measured along the filament.
 5. A process as in claim 1 in which the spray solution comprises the same polymer from which the yarn is made dispersed in a suitable solvent.
 6. A process as in claim 1 in which the spray solution comprises the polymer of which the yarn is made, but in a form chemically modified by substitution of side groups, so as to increase its solubility.
 7. A process as in claim 1 in which the spray solution comprises a rubber polymer.
 8. A process as in claim 1 which further comprises fabricating said yarn into a fabric, garment or article and heat setting the fabric, garment or article made from the yarn.
 9. A process as in claim 8 wherein the solution of polymer is capable of cross-linking with itself or with the yarn, and which further comprises chemical treatment of the fabric, garment or article after, or in the process of, heat setting to cause said cross-linking. 